HOUSTON — The first of two spacewalks by NASA astronauts to replace a failed ammonia pump on the International Space Station has been moved to Saturday, Aug. 7. A second spacewalk is planned for Wednesday, Aug. 11, to complete the repairs.

Teams of flight controllers, engineers, and spacewalk experts have made significant progress in preparing for the first spacewalk, but need an additional day to get ready. The additional time allows for final procedures to be sent late Thursday to the station, giving the crew a full day to review the plans developed by Mission Control. Managers also moved the second spacewalk to Wednesday to give the crew more time to rest and prepare.

Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson are scheduled to perform the spacewalks, which will air on NASA Television. Coverage will begin at 5 a.m. CDT. The spacewalks are scheduled to begin at 5:55 a.m. Saturday’s spacewalk will be the fourth for Wheelock and the first for Caldwell Dyson.

Approximately two hours after the conclusion of each spacewalk, NASA TV will broadcast a briefing from NASA’s Johnson Space Center. The briefing participants will be Mike Suffredini, International Space Station program manager; Courtenay McMillan, Expedition 24 spacewalk flight director; and David Beaver, Expedition 24 spacewalk officer.

Johnson’s newsroom will be open for credentialed reporters to attend the briefing. Johnson also will operate a telephone bridge for reporters with valid media credentials issued by a NASA center. Journalists planning to use the service must contact the Johnson newsroom at 281-483-5111 no later than 15 minutes prior to the start of a briefing. Phone bridge capacity is limited and will be available on a first-come, first-served basis.

Engineers and flight controllers continue to review data on the July 31 pump failure, which caused the loss of one of two cooling loops aboard the station. This failure resulted in a power down and required adjustments to maintain as much redundancy as possible for the station systems. The systems are stable, and the station’s six crew members are not in any danger.

For NASA TV streaming video, schedules and downlink information, visit: http://www.nasa.gov/ntv

For more information about the station and the Expedition 24 crew, visit: http://www.nasa.gov/station